1. Field of the Invention
The present invention generally relates to exposure methods and apparatuses, and, more particularly, to an exposure method and apparatus for patterning a panel such as a reticle or a flat panel display used in the photo process in semiconductor production.
With an exposure apparatus using laser beams, the area irradiated with beams in one scan is limited. The area exposed by one scan is called a field, and a pattern is formed by a plurality of continuously formed fields. To achieve high-precision production, it is necessary to reduce errors in intermediate areas between the fields and accommodate larger exposed areas.
2. Description of the Related Art
In a conventional laser exposure apparatus for patterning the panel of a flat panel display such as a plasma display panel, a laser beam is divided into a plurality of beam elements by a beam splitter. On-off control is performed on each laser beam by an optical modulator in accordance with exposure data. The on-off controlled laser beams are applied to a rotating polygon, and the laser beams reflected by the polygon are then applied to an exposure substrate via a condenser lens. The exposure substrate is scanned in synchronization with the rotation of the polygon.
As shown in FIG. 1, on a 42-inch plasma display panel (PDP), a vertical line (Y direction) can be drawn in one scan by a condenser lens having a diameter of 600 mm. Japanese Laid-Open Patent Application No. 7-35994 discloses such a laser exposure apparatus.
Japanese Laid-Open Patent Application No. 62-26819 discloses a laser exposure apparatus for reticle production. In the laser exposure apparatus, the patterned area on the exposure substrate is exposed twice, four times, or eight times, so as to improve the accuracy in patterning.
As plasma display panels have been becoming larger, the exposure substrates have also been becoming larger; from 42 inches to 55 inches, from 55 inches to 60 inches. To expose a 55-inch exposure substrate, for instance, a condenser lens having a diameter of 750 mm is necessary, as shown in FIG. 2. Even with the 600-mm condenser lens shown in FIG. 1, the resolution at the periphery of the lens is too low.
FIG. 3 shows the relationship between design rule and errors. As shown in the graph, the errors at the scan-start point and the scan-end point corresponding to the lens periphery are larger than the error in the scan center point corresponding to the center area of the lens. Accordingly, accurate patterning with a condenser lens having a diameter of 600 mm or larger is very difficult. Even if fields are continuously formed in the scanning direction, there might be deviations in the intermediate portions between the fields. FIG. 4A shows a case where a deviation is caused between two fields in a Y direction, and FIG. 4B shows a case where a deviation is caused in an X direction. It should be understood that the X-direction deviation and the Y-direction deviation might occur at the same time. FIG. 4C shows a case where a great difference in width is caused in the intermediate area between two fields.
The X-direction deviation and the Y-direction deviation can be corrected by a laser interferometer or an optical modulator to improve the accuracy. However, the difference in width is largely due to the resolution of the lens, and therefore is difficult to eliminate.
With the conventional exposure apparatus that exposes the exposure substrate several times, there is also a problem that the exposure time required by the exposure apparatus is several times longer than a normal exposure time.
A general object of the present invention is to provide exposure methods and apparatuses, in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an exposure method and an exposure apparatus which can prevent differences and irregularities in size and width of the intermediate area without prolonging the exposure time.
The above objects of the present invention are achieved by an exposure apparatus comprising: a rotatable polygon which reflects laser beams to an exposure substrate through a lens: and a discontinuous exposure unit which discontinuously exposes the scan-end point in a first field to be scanned on the exposure substrate, and discontinuously exposes the scan-start point in a second field to be scanned on the exposure substrate. Here, the exposure substrate is moved so that the scan-end point in the first field and the scan-start point in the second field overlap with each other to form an intermediate area.
With this structure, the exposure of the first field and the exposure of the second field are averaged in the intermediate area. Thus, differences and irregularities in width can be avoided in the intermediate area.
The above objects of the present invention are also achieved by an exposure apparatus comprising: a rotatable polygon which reflects laser beams to scan an exposure substrate through a lens; and a rotation unit which rotates the exposure substrate through an angle of 180xc2x0 after a first field to be scanned on the exposure substrate is exposed. Here, a second field to be scanned on the exposure substrate is exposed after the exposure substrate is rotated through an angle of 180xc2x0, so that the scan-end point in the first field becomes continuous with the scan-start point in the second field.
With this structure, the scan-end point in the first field and the scan-start point in the second field can be exposed with the same part of a lens. Thus, differences in size and width due to irregular resolution of the lens can be prevented in the intermediate area.
The above objects of the present invention are also achieved by an exposure apparatus comprising: a rotatable polygon which reflects laser beams to scan an exposure substrate through a lens; a first lens which is used to expose a main pattern in the center of the exposure substrate in a scanning direction; and second and third lenses which are used to expose peripheral patterns adjacent to the scan-start point and the scan-end point, respectively, of the main pattern in the center of the exposure substrate.
With this structure, the exposure is performed with the center part of each lens. Thus, differences in size and width due to irregular resolution of the lens can be prevented in the intermediate area.
The above objects of the present invention are also achieved by an exposure method comprising the steps of:
irradiating an exposure substrate with laser beams reflected from a rotatable polygon through a lens;
discontinuously exposing the scan-end point in a first field to be scanned on the exposure substrate;
moving the exposure substrate so that the scan-end point in the first field and the scan-start point in a second field to be scanned overlap with each other to form an intermediate area to be exposed; and
discontinuously exposing the scan-start point in the second field on the exposure substrate.
By this method, the exposure of the first field and the exposure of the second field are averaged. Thus, differences in size and width can be prevented in the intermediate area.
The above objects of the present invention are also achieved by an exposure method comprising the steps of:
irradiating an exposure substrate with laser beams reflected from a rotatable polygon through a lens;
exposing a first field to be scanned on the exposure substrate;
rotating the exposure substrate through an angle of 180xc2x0, so that the scan-end point in the first field becomes continuous with the scan-start point in a second field to be scanned on the exposure substrate; and
exposing the second field on the exposure substrate.
By this method, the scan-end point in the first field and the scan-start point in the second field can be exposed with the same part of a lens. Thus, differences in size and width due to irregular resolution of the lens can be prevented in the intermediate area.
The above objects of the present invention are also achieved by an exposure method comprising the steps of:
irradiating an exposure substrate with laser beams reflected from a rotatable polygon through a lens;
exposing a main pattern in the center of the exposure substrate in a scanning direction with a first lens; and
exposing peripheral patterns of the exposure substrate with second and third lenses, the peripheral patterns being adjacent to the scan-start point and the scan-end point, respectively, of the main pattern in the center of the exposure substrate.
By this method, the exposure is performed with the center part of each lens. Thus, differences in size and width due to irregular resolution of the lenses can be prevented in the intermediate area.
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.